The turn of the large(ish) scope - Crescent Nebula

[GavStar]

After last weeks’ fun night vision observing sessions with my 60mm scope last week, I decided to go to the other aperture end of my scope collection and bring out the Celestron C11. 

SCTs do seem to get somewhat of a bad press compared to dobs and refractors. But I have been pleasantly surprised by this scope in the three months or so I’ve had it. The aim was to get aperture in a portable relatively easy to mount way and I think it achieves this pretty well.

In the end, though, it was a frustrating evening with fast moving blankets of cloud covering up some nice (for SW London) clear skies.

However, I did have one success - my first observation of the crescent nebula. I used just my 55mm plossl and so was operating at a relatively fast (for night vision) f ratio of 5. But this gave a higher magnification of 50x and so framed the nebula nicely and made the detail easier to see (if a bit noisy). Some really nice Veil like tendrils were visible. It wetted my appetite for this emission nebula and I’ll be aiming to observe it again in the next month or so when hopefully conditions are better.

Phone pic attached.

 

[jetstream]

Great report Gavin!

Can't wait for your upcoming dark site trip...!

[alanjgreen]

Nice image.

If you can imagine the brightness turned up by about x20 then that's what I get with big dob and NV (from my darker sky location which does make a difference - I do not buy into this theory that NV is only for city based observers at all  ). The Crescent really is bright with the 20", especially that claw section on the right hand side. There is lovely dark black detail within all this bright nebula section. The whole thing takes on the appearance of an inverted number 9, which is just coming through in your image.

- The Crescent also delivers well in the Borg89 too, it really is a winner in any scope with NV but the extra scale gives the finer details of course.

Give the Wizard (NGC4380) a try next time and see if you see the "horse". Also don't forget the Bubble with the C11 - that should be good too at the higher magnification.

The other thing that may be interesting to do would be to get images of the same object using all your scopes then you could publish a scope by scope comparison/medley all taken from the same observing site? 

Alan

[GavStar]

35 minutes ago, alanjgreen said:

Give the Wizard (NGC4380) a try next time and see if you see the "horse". Also don't forget the Bubble with the C11 - that should be good too at higher magnification.

I did get the wizard (NGC7380?) for a bit. Was a bit faint under my skies and the higher f ratio though (see below)

 

[alanjgreen]

49 minutes ago, GavStar said:

I did get the wizard (NGC7380?) for a bit. Was a bit faint under my skies and the higher f ratio though (see below)

Argh, its upside down & reversed compared to my view :(   Not sure you will see the "horse" very easily in this reversed image.

You got the two humps of the "camels back" (7 o clock position). In the dob view these are at 12 o'clock above the horse (at first it looked like a "jockey" on the horses back. The horse's head is buried in the "bright area" at the bottom and can just make it out. The black body is running away vertical in your image towards the double star.

Still, pretty decent view considering your location.

[Stu]

This may be the ‘correct’ way round. I flipped it horizontally to make it as per naked eye view, then rotated 180 degrees to give dob view. I can see a kind of pantomime horse now...

 

[alan potts]

The SC does get a fair lot of bad press as you asy, my only gripe with them is the focal length never allowing more than just shy of 1 degree no matter which eyepiece you use. In general though they are jolly good scopes as long as you keep that collimation spot on. I took mine out of the observatory in favour of the APO for AP work, but now I have put it back, just couldn't get on with the APO there on the AZ EQ 6, glad I didn't buy that larger mount now.

Nice images BTW.

Alan

[jetstream]

16 hours ago, GavStar said:

SCTs do seem to get somewhat of a bad press compared to dobs and refractors. But I have been pleasantly surprised by this scope in the three months or so I’ve had it.

You are sure getting some great results with the NV and also the SCT Gavin, nothing wrong with SCT's thats for sure!

[PeterW]

Nowt wrong with anything as long as it’s fast... slightly shocked I hear a die hard refractor user posting about a reflector ? !

i wonder if you could use an f6.3 SCT reducer and then pop the 55mm afocal into it??? Faster still!

PEter

[GavStar]

18 minutes ago, PeterW said:

i wonder if you could use an f6.3 SCT reducer and then pop the 55mm afocal into it??? Faster still!

PEter

Peter, I do have a 0.75 AP photo visual reducer which takes the f-ratio down to a more respectable 3.75 and this works well. However last night I wanted to get the image scale up on the crescent to get some more detail.

Another day when I have more time and better skies I will do a side by side comparison of f3.75 vs f5.

[jetstream]

3 hours ago, GavStar said:

However last night I wanted to get the image scale up on the crescent to get some more detail.

It worked

I can't wait until you get this figured out for me

 

[niallk]

Very cool Crescent neb!  

[alan potts]

9 hours ago, PeterW said:

Nowt wrong with anything as long as it’s fast... slightly shocked I hear a die hard refractor user posting about a reflector ? !

i wonder if you could use an f6.3 SCT reducer and then pop the 55mm afocal into it??? Faster still!

PEter

Peter, you can't, I made that mistake 10 years ago, bought the LX200 12 inch, and a 40mm SWA as well as the reducer and thought I would be able to see my feet. You can only go down to 27 mm 68degrees with the redicer before you get vignetting. I also got away with the 24mm 82degree Meade UWA. Never use it now, the reducer that is.

[Stu]

20 minutes ago, alan potts said:

Peter, you can't, I made that mistake 10 years ago, bought the LX200 12 inch, and a 40mm SWA as well as the reducer and thought I would be able to see my feet. You can only go down to 27 mm 68degrees with the redicer before you get vignetting. I also got away with the 24mm 82degree Meade UWA. Never use it now, the reducer that is.

It may still work for NV though Alan, which is about the speed of the system rather than FOV. The NV unit has a limiting field stop anyway so vignetting from the reducer may not be an issue.

[RobertI]

These are stunning results, frankly it's just not fair. 

@GavStar and @alanjgreen - are either of you going to Kelling Heath? I'd just love to have a squint through one of these NV setups.

[PeterW]

Sometimes vignetting is masked by the roll off of hydrogen nebula brightness across the image caused by the filter response as it gets used with increasingly off axis light. Thanks for the heads up.

Peter

[GavStar]

1 hour ago, RobertI said:

These are stunning results, frankly it's just not fair. 

@GavStar and @alanjgreen - are either of you going to Kelling Heath? I'd just love to have a squint through one of these NV setups.

Robert

Unfortunately not. 

Also I was booked up for the SGL party this October but unfortunately had to cancel as my girlfriend booked me a birthday surprise outing for the same weekend!!

However I am intending to go on at least one, maybe two next year. I’d really like to meet more members of SGL and also to see what others think of night vision.

[John]

1 hour ago, GavStar said:

.... and also to see what others think of night vision.

I wonder if I could get a grant towards the cost of LV from my local authority who has put all these lights in my town 

Might be worth a cheeky letter

 

[PeterW]

... though you’d settle for them spending the same amount on proper lighting shields... I’m sure they’d save more than enough if they used dimming and part lighting like the council near where we meet up..l

Tell us how you get on!

PEter

[RobertI]

3 hours ago, GavStar said:

Robert

Unfortunately not. 

Also I was booked up for the SGL party this October but unfortunately had to cancel as my girlfriend booked me a birthday surprise outing for the same weekend!!

However I am intending to go on at least one, maybe two next year. I’d really like to meet more members of SGL and also to see what others think of night vision.

Keep us posted on your Kelling Heath (or other star party plans). I live within a couple of hours’ drive of Kelling Heath so can whizz up if it’s clear. ?

[alan potts]

6 hours ago, Stu said:

It may still work for NV though Alan, which is about the speed of the system rather than FOV. The NV unit has a limiting field stop anyway so vignetting from the reducer may not be an issue.

Maybe Stu but the point I made after a fair bit of research was purely with regards to eyepieces. In view of the fact the only issue I saw was vignetting then with a NV unit, which I know nothing about, it may well work. Though I am fair;ly sure FOV with be restricted somewhat..

Alan

[Stu]

7 minutes ago, alan potts said:

Maybe Stu but the point I made after a fair bit of research was purely with regards to eyepieces. In view of the fact the only issue I saw was vignetting then with a NV unit, which I know nothing about, it may well work. Though I am fair;ly sure FOV with be restricted somewhat..

Alan

Understood Alan. If I remember correctly, you have to assume something like a 40 degree afov for NV so it is likely to be the limiting factor, not the reducer.

[GavStar]

6 minutes ago, Stu said:

Understood Alan. If I remember correctly, you have to assume something like a 40 degree afov for NV so it is likely to be the limiting factor, not the reducer.

I’ll try my 0.75 reducer sometime and post some photos to show what impact it has for NV - from memory it’s ok due to the lower fov but my memory is a bit fuzzy 

[Special K]

Great Crescent. How many times have I tried to see thee?!!!!  This is the one that always gets away.  

Personally I’d like an SCT hanging around for variety. Well done!

[PeterW]

Can see it in a newt too.. whatever gives you sufficient scale. 

Peter